Concentration of slurries



Dec. 12; 1944.

H. G. L-AUGHLIN ETAL CONCENTRATION OF SLURRIES Fi'led March ,24, 1941 Patented Dec. '12, 1944 CONCENTRATION OF SLURRIES Herman G. Lauglilin, Tonawanda. and Gerald J.

Kisser, Niagara Falls, N. Y., assignors to E. I. du Pont de Nemours & Company, Wilmington,

. Del., a cornorationof Delaware Application March 2}, 1941, Serial No. 384,926 I 14 Claims. (cram-s) 1 This invention relates to the concentration of slurries and particularly to a'novel apparatus for the concentration of slurries.

In the purification of salts such as' sodium chloride it is usually necessary 'to use large volto recover the purified salt. Ordinarily this may be accomplished by evaporating solutions of the salts to obtain a dilute slurry, concentrat-' ing to a heavy slurry by means of large settling equipment, filtering to remove the solid salt, and repeating these operations. During the-concenmoved by passing the dilute slurry through settlers at low velocity. Conventional settlers are umes of water which must be removed in order Referring to Figure i I, is avertical cylindrical,-

body with its lower part ending in a conduit. 2 is an' inlet connected tangentially to the upper part of the cylindrical body and extending to helical baflle 4 which surrounds the concentric vertical conduit 3. 5 is the .concentric vertical bafile in preferred form.

trating operation large volumes of liquid are re costly and require'considerable floor space. Due

to the large volumes and surfaceareas required, serious heat losses occur by radiation and convection and must be replaced in the subseqent evaporation step. Such losses of heatnecessarily add to the cost of the purified material."

In the operation of ourv invention the' slurry to be concentrated is forced by a pump, gravity,.or other means throughin'let 2 and follows the helical passage defined by baiiie 4. During the rotation of the slurry, the solid particles are forced to the outside and follow a path ache..- cent the circumference of the cylindrical separator, whilethe comparatively clear liquid re mains in that section .of the separator near the circumference of the vertical conduit. The ver-.,

- tical 'baflie I separates the. concentrated slurry It is one of the objects of this invention'to pro-' vide a novel and practical method and apparatusfor the concentration of slurries. 'A further ob-- ject is to provide a means for the' concentration of slurries which is-simple, efllcient, and suitable for rapid and continuous operation.- These and other objects will be apparent from the ensuing description of our invention.

These objects are attained in accordance 'with our invention by providing a centrifugal separator of novel design. The centrifugal separator of our invention'comprises a'vertical 'cylind'rical body having a closed-top and an inletconnected tangentially to its upper part.

I A vertical conduit is situated concentrically withinthe body of I the separator and extends through the top thereof. A vertical baflle of circular horizontal crosssection and concentric with the cylindrical wall -of the separator is located at the lower extremity of the vertical conduit We have further discovered that even more efficient action is obtained by the arrangement of a bafile situate'd'in the annular space between the vertical conduit and the wall of the separator so arranged as to form a substantially. helical passageway through the 'major portion of the annular space.

Our invention is.illustrated by the accom panying drawings .inwhich Figure 1 isa vertical section of our novel centrifugal separator nular space between the vertical conduit and the wall of the separator and in one modification -of our invention the concentric ;baiile may be arranged entirely below the'lower extremity of the vertical conduit. Preferably the-*baille is located at least partially within the annular space 4 vention.

from the comparatively clearliquor and the lat-. ter rises, and;leaves-the separator through the vertical conduit t-while the concentrated slurry exits through the outlet inthe bottom of the separator. The separator is operated so as to be completely filled during operation. The rate at which the slurry is fed may be regulated so as v to obtain thedesired degree of separation- It has been found that the upper-extremity ofthe concentric bailie'illustrated at 5 must have a diameter greater than the diameter. of theopening in the verticalconduit and this feature is essential to the successful operation of our in- Furthermore,-we have found that the most efficient concentration is obtained when this concentric baiile has the shape ofthe' inverted-fru'stuin of a cone, as shown in the drawlugs and, in a preferred embodiment, the minimumdiameter of this baflie islgreater than the diameter of "the lower extremity of the vertical conduit. The concentric baifleis located at the lower extremity of the vertical conduit and may be either completely or partially within, the an- 4 between thevertical conduit and the wall ofthe in'preferred form and Figure 2 is a horizontal section along lines 2-2 of Figure 1. sponding parts in Figs. 1 and 2 have likeireference numbers. I j

Correarrangement.

bailie is to separate concentrated slurry and come. paratively clear liquor and to deflect the latter'- separator and extends below the'lower extremity ofthe vertical conduit since we have found that the most eflicient operation "is obtained with this The function of this concentric intothe vertical conduit.v This baiiie may be fastened to the vertical conduit by means of rods or narrow strips.

In a preferred form of our invention as illustrated in Figure l the vertical conduit is surrounded by a substantially helical baflle the function of which is to insure adequate and directional rotation of the incoming slurry. Furthermore, in the preferred embodiment of our invention illustrated, the inlet 2 extends through the wall of the separator and provides an enclosed passage to the entrance of the helical passage defined by baflie 4, thus preventing change in the direction of flow of incoming slurry before entering the helical passage. Such an arrangement tends to prevent turbulent flow within the space between the inletand the vertical conduit and consequent loss in efliciency. The number of turns in this helical baflle may vary considerably for the concentration of different slurries, and also may be adjusted to produce the most eificient results with a given rate of ,flow. For instance, we have found that a helical baflle having four complete turns around the vertical conduit is very efiective in concentrating a salt slurry containing about 5% solids and, in a preferred embodiment of our invention, the helical bafile contains not less than ,four complete turns since we have discovered that a baflle having less than four complete turns is not as eflicient for concentrating such slurries as is a helical baflle having four or more complete turns.

The centrifugal separator of our invention may be constructed of any suitable material which' will be apparent to those skilled inv the art and whereas in the apparatus of the present invention little or no crystal growth is possible because of thecomparatively high velocity utilized.

Utilization of our invention reduces heat losses to a minimum and this is an important factor, particularly in large scale operation.

Other advantages and modifications will be apparent to those skilled in the art without departing from the scope of our invention.

I claim:

1. A centrifugal separator comprising a vertical hollow cylinder having a closed top, an inlet connected with said vertical hollow cylinder in its upper part, said inlet being so arranged as to lead fluid into said vertical hollow cylinder in a substantially tangential direction, a vertical eilluent conduit situated concentrically within said vertical hollow cylinder and extending through the top of said vertical hollow cylinder, an annular space lying between said etlluent conduit and the interior circumferential surface of said vertical hollow cylinder, helical baflle means situated in said annular space, said helical baille means being so arranged in relation to said vertical conduit and the interior circumferential surface of said vertical hollow cylinder as to define a substantially helical passageway throughout at least the major part of said annular space and a vertical baflle of circular horizontal cross-section located concentrically within the lower part of said annular space below said helical bafile means and extending below the lower end of said vertical conduit, the diameter of the upper extremity of said vertical baiile being greater than the diameter of the lower extremity of said vertical conduit, and an outlet at the bottom of said vertical hollow cylinder.

2. The apparatus of claim 1 wherein said bafile of circular horizontal cross-section is the shape of an inverted frustum of a cone.

3. A centrifugal separator comprising a vertical hollow cylinder having a closed top, an inlet connected with said vertical hollow cylinder in its possible to obtain slurries of much higher concentration where desirable. With suitable regulation our invention may also be effectively used as a classifier.

The apparatus of our invention is economical to install and maintain because it is simple to construct and contains no moving parts. It requires little space and avoids the necessity for storing large volumes of slurry. Thus the system I may be drained without substantial losses in material when operation is interrupted. A further important advantage of our centrifugal separator resides in the fact that the concentration of slurries is carried out in a closed system thus avoiding aeration which in many cases causes an increase in the corrosive action of the liquor and consequent increase in the cost of maintaining equipment.

The centrifugal separator of our invention may be operated at any desired pressure and is therefore readily adaptable to various types'of operation. The degree of concentration may be controlled by regulating the rate of concentrate removal and it is therefore possible to obtain a specified concentration of slurry.

In large settling tanks such as are commonly used for the concentration of slurries the time required for proper concentration permits crystal growth which may be undesirable because of inclusion of impurities or variation in particle size upper part said inlet being so arranged as to lead fluid into said vertical hollow cylinder in a substantially tangential direction, a vertical eflluent conduit situated concentrically within said vertical hollow cylinder and extending through the top of said vertical hollow cylinder, an annular space lying between said efiiuent conduit and the interior circumferential surface of said vertical hollow cylinder, a helical baffle having at least four complete turns situated in said annular space said helical bailie having at least four complete turns being so arranged in relation to said vertical conduit and the interior circumferential surface of said vertical hollow cylinder as to define a substantially helical passageway throughout at least thevmajor part of said annular space, and a vertical baille of circular horizontal crosssection located concentrically within the lower part of said annular space below said helical baflie and extending below the lower end of said vertical conduit, said vertical bafile having a minimum diameter greater than the diameter of the lower extremity of said vertical conduit, and an outlet at the bottom of said vertical hollow cylinder.

4. A centrifugal separator-comprising a vertical hollow cylinder having a closed top, an inlet connected with said vertical hollow cylinder in its upper part said inlet being so arranged as to lead fluid into said vertical hollow cylinder in a substantially tangential direction, a vertical eflluent conduit situated concentrically within said vertical hollow cylinder and extending through the top of said vertical hollow cylinder,

accuse and a vertical baille of circular horizontal crosssection located concentrically with, and at the lower extremity of, said vertical conduit thediameter of the upper extremity of said vertical baflle being greater than the diameter of the lower'ex'tremity of said vertical conduit, and an cylinder.

5. The apparatus of claim-1 wherein said baille of circular horizontal cross-section is the shape 4 of an inverted frustum of a cone.

6. A centrifugal separator comprising a vertical hollow cylinder having a cl'osed'top, an'inlet outlet at the bottom of said vertical hollow the lower end of said eflluent conduit the diameter of the upper extremity of said concentric baffle being greater than the diameter of the lower extremity of said cylindrical eilluent conduit,

connected with said vertical hollow cylinder inits upper part said inlet being so arranged as to lead fluid into said vertical hollow cylinder in a substantially'tangential direction, a cylindrical eflluent conduit within and concentric with said vertical hollow cylinder and extending through the top of said vertical hollow cylinder, an anand an outlet at the bottom of said vertical hollow cylinder. Y

10. Theapparatus of claim 9 wherein said baflle, of substantially circular horizontal cross-.

section is theshape of an inverted frustum of a nular space lying between said eflluent conduit and the interior circumferential surface of said vertical hollow cylinder, helical baflle means situatedin said annular-space said helical baflle means being so arranged in relation to said emuent conduit and the interior circumferential surface of said vertical hollow cylinder as to define a substantially helical passageway through-- out at least the major part of said annular space, and a vertical baflle of circular. horizontal crosssection located concentrically within the lower part of said annular space below said helical baffle means and extending below the lower end of said efllunt conduit, the diameterof the upper extremity of said vertical baflle being greater.

. than the diameter of 'the lower extremity of said effluent conduit, and an outlet at the bottom of said vertical hollow cylinder.

7. A centrifugal separator comprising a vertical hollow cylinderhaving a closed ,top, an inlet connected with said vertical hollow cylinder in its upper part said inlet being so arranged as to lead fluid into said vertical hollow cylinder in a substantially tangential direction, a cylindrical eiiluent conduit within and concentric with said vertical hollow cylinder and extending through the top of said vertical hollow cylinder, an annular space lying between said eflluent con.- duit and the interior circumferential surface of said vertical hollow cylinder, helical batlle means situated in said annular space said helical baflle means being so arranged in relation to said eilluent conduit and the interior circumferential surface of said vertical hollow cylinder as to define a substantially helical passageway throughout at least the major part of said annular space, and a concentric baiile of substantially circular extremity of said annular space and extending below the lower end of said efiluent conduit, said concentric baille having -a minimum diameter greater than the diameter of the lower extremity of said cylindrical eilluent conduit, and an outlet at the bottom of said vertical hollow cylinder.

8. The apparatus of claim '7 .wherein said 11. A centrifugal separator comprising a vertical hollow cylinder having a closed top, an inlet connected with said vertical hollow cylinder inits upper part said inlet being so arranged as to lead fluid into said vertical hollow cylinder in a I substantially tangential direction, a vertical effluent conduit situated concentrically within said vertical hollow cylinder and extending through the top of said vertical hollow cylinder,

an annular space lying between said effluent conduit and the-interior circumferential surface of said vertical 'hollowcylinder, helical baflle means situated in said annular space said helical bailie -means being so arranged in relation to said verticalconduit and the interior circumferential surface of said vertical hollow cylinder as todeflne a substantially helical passageway throughout at least-the major part of said. annular space,

said inlet extending to the entrance to said substantially helical passageway ahd a vertical baille of circular horizontal cross-section located c0n-,

.of the lower extremity of said vertical conduit,

and an outlet at the bottom of said vertical hollow cylinder.

' horizontal cross-section located within the lower baille of substantially circular horizontal crosssection is the shape of an inverted frustum of a cone.

9. A centrifugal separator. comprismg a versageway throughout at least the major'part of Y tical hollow cylinder having a closed top, an inlet connected with said vertical hollow cylinder in its upper part said inlet being so arranged as to lead fluid into said vertical hollow cylinder in a substantially tangential direction, a cylindrical 12. The apparatus of claim 11 wherein said battle of circular horizontal cross-section is the shape of an inverted frust'um of a cone.

13. A centrifugal separator comprising -a vertical hollow cylinder having a closed top, an inlet connected with said vertical hollow cylinder in its upper part said inlet .being so arranged as to lead fluid into said vertical hollow cylinder' in a substantially tangential direction, a vertical eflluent conduit situated concentrically within said vertical hollow cylinder and extending through the top of said vertical hollow cylinder, an annular space lying betweensaid. efliuent coridult and the interior circumferential surface of said vertical hollow cylinder, a helical baffle having at least four complete turns situated in said annular space said helical baille having at least four complete turns being 'so arranged in relation to said vertical conduit and theinterior circumferential surface of said vertical hollow cylinder as to define a substantially helical passaid annular space, said inlet extending to the entrance to said substantially helical passage-,-

way, and a vertical baille of circular horizontal cross-section located concentrically within the lower part of said annular space below said helical baiile and extending below the lower end.

per extemity of said vertical balile being greater than the diameter of the lower extremity of said vertical conduit, and an outlet at the bottom of said vertical hollow cylinder.

14. A centrifugal separator comprising a ver- 2,864,799 I v I eflluent conduit and the interior circumferential surface of said vertical hollow cylinder as to define a substantially helical passageway throughout at least the major part of said annular space said inlet extending'to the entrance to said substantially helical passageway and a vertical baffle of circular horizontal cross-section located concentrically within the lower-part of said annular space below said helical baille means and extending below the lower end of said eiiluent conduit, the diameter of the upper extremity of said vertical baffle being greater than the diameter of the lower extremity of said emuent conduit;

and an outlet at thebottom of 'said vertical hollow cylinder.

' HERMAN G. LAUGHIJN.

GERALD J. RISSER. 

